The present invention relates to welding devices and is particularly concerned with an improved shielded-arc welding torch for internally welding tubes to tube sheets or headers, such as are commonly found in the heat exchangers of various power plants.
In the manufacture and repair of industrial and electrical utility power plants, automated welding equipment has been employed to provide consistently high quality welds of internal tube-to-header joints in the heat exchangers of the power plants. Such internal tube-to-header joints generally afford unobstructed access that permits placement of a welding torch without the need for handling by a welder. This facilitates proper positioning of the welding torch at the joint prior to welding and assists in maintaining proper alignment of the torch with respect to the joint during the welding cycle. Accordingly, without a requirement for manual placement of the torch and its associated physical burdens, highly reliable welds are regularly produced.
Many internal tube weld joints, however, are located in very confined spaces of limited accessibility. These difficult-to-reach tube-to-header joints, such as those located in the superheater boilers of ship propulsion systems, generally require manual positioning and support of the welding torch throughout the welding cycle. As a result, unsatisfactory and incomplete welds are evidenced at these relatively inaccessible joints due to either a failure by the welder to initially position the torch properly or his inability to maintain the proper alignment of the torch in the tube while welding.
While existing internal tube welding torches have proven satisfactory in welding the easily accessible tube-to-header joints of various heat exchanger systems, those torches have not been entirely adequate in producing consistent, high quality welds of such joints in closely confined spaces. Previously designed torches have not been able to relieve the physical strains of manually maneuvering the torch into its proper welding position within the confined space and thereafter, continuously supporting the torch in the proper position while welding.